In the past only the following processes for producing NDC's by hydrocyanation of BHC were known:
(i) A process where a catalyst system comprising a cobalt carbonyl catalyst and triphenyl phosphine is used (see U.S. Pat. Nos. 2,666,780 and 2,666,748). PA0 (ii) A process where a catalyst system composed of tetrakis (triaryl phosphite) palladium and triphenyl phosphite is used (Am. Chem. Soc. Div. Pet. Chem. Preprints, 14, B 29 (1969), etc. PA0 (iii) U.S. Pat. No. 3,496,217 discloses a process for producing dinitriles such as adiponitrile and the like which comprises hydrocyanation of olefins such as 3-pentenenitrile, 4-pentenenitrile and the like in the presence of a zero-valent nickel complex and a promoter such as zinc chloride and the like. PA0 (iv) U.S. Pat. Nos. 3,655,723 and 3,766,237 disclose examples where a zero-valent nickel complex and zinc chloride are used upon hydrocyanation of methyl bicyclo (2,2,1)-5-heptene-2-carboxylate as a bicyclo (2,2,1)-5-heptene compound, and U.S. Pat. No. 3,752,839 discloses examples using a zero-valent palladium catalyst and zinc chloride catalyst system. PA0 (v) Examples using a zero-valent nickel complex and zinc chloride are disclosed in U.S. Pat. Nos. 3,850,973 and 3,925,445 which are directed to a process for producing cyanoolefins by hydrocyanation of butadiene and bicyclo (2,2,1)-2,5-heptadiene, and in U.S. Pat. No. 4,215,068 which is directed to a process for producing a dicyanocyclopentane by hydrocyanation of cyclopentadiene and then hydrocyanation of the resulting product, cyanocyclopentene.
However, it can not be said that prior art has proposed a satisfactory process for producing NDC's.
For example, in (i) above, the yield of NDC's is only about 62% when a cobalt catalyst and triphenyl phosphine are used in an amount of 15-30% by weight based on BHC and hydrogen cyanide is used in a large amount, that is, 1.4 time that of BHC followed by carrying out the reaction at 130.degree. C. for 8 hours.
According to the production process of (ii) above, since an expensive palladium catalyst is used, recovery of the catalyst is troublesome, and the reaction temperature is so high (150.degree.-190.degree. C.) that handling is difficult, and further, as is clear from the low yield, the catalytic activity is low.
In the hydrocyanation of olefins and dienes in (iii) and (v), a zero-valent nickel complex is used in a large amount, i.e. about 0.5-2.5 mol % based on the olefin while the conversion of olefins and dienes is 30-80% and the yield of the end product, dinitriles, is as low as 30-70%. In addition, products and yields are not disclosed in the hydrocyanation of bicyclo (2,2,1)-5-heptene compounds in (iv) above.
An object of the present invention is to solve the above-mentioned problems of the prior art and produce NDC's at a high conversion, high selectivity and advantageously from an economical point of view.